In conventional arc welding, when aluminum is welded, a welding voltage and a weld wire supply speed at a welding start period are set to be the same as those at a steady welding period. At a welding end period, in order to repress generation of a crater, the welding voltage is reduced from a level at the steady welding period to a crater processing level, and the supply speed of the weld wire is reduced according to the reduction in the welding voltage. As the conventional arc welding, arc welding in Patent Document 1, for example, is known.
In the conventional arc welding, as shown in FIGS. 8A to 8C, since the welding voltage and the weld wire supply speed at welding start terminal portion 103 are the same as those at steady welding period TN, in the case where base material 101 with low intrinsic resistivity such as aluminum is welded, insufficient penetration occasionally occurs near welding start terminal portion 103 due to insufficient heat. A bead width is narrow, a bead height is high, and weld penetration is shallow, namely, a bead appearance does not have fitting of a bead.
The generation of crater 102 at a welding end portion can be reduced by controlling the welding voltage and the wire supply speed. However, only when welding voltage V1 and wire supply speed WS1 at steady welding period TN are adjusted so as to be welding voltage V2 and wire supply speed WS2 at a welding end point, occasionally crater 102 cannot be stably formed. This is because in the case where a weld wire is moved in a welding direction at end period TE at the same welding speed as that at steady welding period TN, if the weld wire supply speed is reduced from WS1 to WS2, a supply amount of the weld wire is reduced and the bead width becomes too thin. Therefore, a welding method which can secure a welding quality on a whole welding length from the welding start terminal portion to the end portion is desired.
Patent Document 1: Unexamined Japanese Patent Publication No. H1-107968